=================
Conflict handling
=================

Some operations, like merge, revert and pull, modify the contents of your
working tree.  These modifications are programmatically generated, and so they
may conflict with the current state of your working tree. Many kinds of changes
can be combined programmatically, but sometimes only a human can determine the
right thing to do.  When this happens Bazaar will inform you that there is a
conflict and then ask you to resolve it.  The command to tell Bazaar a conflict
is resolved is ``resolve``, but you must perform some action before you can do
this.

Each type of conflict is explained below, and the action which must be done to
resolve the conflict is outlined.


Text conflicts
==============
Typical message::

  Text conflict in FILE

These are produced when a text merge cannot completely reconcile two sets of
text changes.  Bazaar will emit files for each version with the extensions
THIS, OTHER, and BASE.  THIS is the version of the file from the target tree,
i.e. the tree that you are merging changes into.  OTHER is the version that you
are merging into the target.  BASE is an older version that is used as a basis
for comparison.

In the main copy of the file, Bazaar will include all the changes that it
could reconcile, and any un-reconciled conflicts are surrounded by
"herringbone" markers like ``<<<<<<<``.

Say the initial text is "The project leader released it.", and THIS modifies it
to "Martin Pool released it.", while OTHER modifies it to "The project leader
released Bazaar."  A conflict would look like this::

  <<<<<<< TREE
  Martin Pool released it.
  =======
  The project leader released Bazaar.
  >>>>>>> MERGE-SOURCE

The correct resolution would be "Martin Pool released Bazaar."

You can handle text conflicts either by editing the main copy of the file, or
by invoking external tools on the THIS, OTHER and BASE versions.  It's worth
mentioning that resolving text conflicts rarely involves picking one set of
changes over the other.  More often, the two sets of changes must be
intelligently combined.

If you edit the main copy, be sure to remove the herringbone markers.  When
you are done editing, the file should look like it never had a conflict, and be
ready to commit.

When you have resolved text conflicts, just run "bzr resolve", and Bazaar will
auto-detect which conflicts you have resolved.

Content conflicts
=================
Typical message::

  Contents conflict in FILE

This conflict happens when there are conflicting changes in the target tree and
the merge source, but the conflicted items are not text files.  They may be
binary files, or symlinks, or directories.  It can even happen with files that
are deleted on one side, and modified on the other.

Like text conflicts, Bazaar will emit THIS, OTHER and BASE files.  (They may be
regular files, symlinks or directories).  But it will not include a "main copy"
of the file with herringbone conflict markers.  It will appear that the "main
copy" has been renamed to THIS or OTHER.

To resolve this, use "bzr mv" to rename the file back to its normal name, and
combine the changes manually.  When you are satisfied, run "bzr resolve
FILE".  Bazaar cannot auto-detect when conflicts of this kind have been
resolved.

Duplicate Paths
===============
Typical message::

  Conflict adding file FILE.  Moved existing file to FILE.moved.

Sometimes Bazaar will attempt to create a file using a pathname that has
already been used.  The existing file will be renamed to "FILE.moved".  If
you wish, you can rename either one of these files, or combine their contents.
When you are satisfied, you can run "bzr resolve FILE" to mark the conflict as
resolved.

Unversioned Parent
==================
Typical message::

    Conflict because FILE is not versioned, but has versioned children.

Sometimes Bazaar will attempt to create a file whose parent directory is not
versioned.  This happens when the directory has been deleted in the target,
but has a new child in the source, or vice versa.  In this situation, Bazaar
will version the parent directory as well.  Resolving this issue depends
very much on the particular scenario.  You may wish to rename or delete either
the file or the directory.  When you are satisfied, you can run "bzr resolve
FILE" to mark the conflict as resolved.

Missing Parent
==============
Typical message::

  Conflict adding files to FILE.  Created directory.

This happens when a file has been deleted in the target, but has new children
in the source.  This is similar to the "unversioned parent" conflict, except
that the parent directory does not *exist*, instead of just being unversioned.
In this situation, Bazaar will create the missing parent.  Resolving this issue
depends very much on the particular scenario.  You may wish to rename or delete
either the file or the directory.  When you are satisfied, you can run "bzr
resolve FILE" to mark the conflict as resolved.

Deleting Parent
===============
Typical message::

  Conflict: can't delete FILE because it is not empty.  Not deleting.

This is the opposite of "missing parent".  A directory is deleted in the
source, but has new children in the target.  Bazaar will retain the directory.
Resolving this issue depends very much on the particular scenario.  You may
wish to rename or delete either the file or the directory.  When you are
satisfied, you can run "bzr resolve FILE" to mark the conflict as resolved.

Path Conflict
=============
Typical message::

  Path conflict: PATH1 / PATH2

This happens when the source and target have each modified the name or parent
directory of a file.  Bazaar will use the path elements from the source.  You
can rename the file, and once you have, run "bzr resolve FILE" to mark the
conflict as resolved.

Parent Loop
===========
Typical message::

  Conflict moving FILE into DIRECTORY.  Cancelled move.

This happens when the source and the target have each moved directories, so
that, if the change could be applied, a directory would be contained by itself.
For example::

  $ bzr init
  $ bzr mkdir a
  $ bzr mkdir b
  $ bzr commit -m "BASE"
  $ bzr branch . ../other
  $ bzr mv a b
  $ bzr commit -m "THIS"
  $ bzr mv ../other/b ../other/a
  $ bzr commit ../other -m "OTHER"
  $ bzr merge ../other

In this situation, Bazaar will cancel the move, and leave "a" in "b".
You can rename the directories if you like, and once you have, run "bzr resolve
FILE" to mark the conflict as resolved.

MalformedTransform
==================
It is possible (though very rare) for Bazaar to raise a MalformedTransform
exception.  This means that Bazaar encounted a filesystem conflict that it was
unable to resolve.  This usually indicates a bug.  Please let us know if you
encounter this.  Our bug tracker is at https://launchpad.net/bzr/+bugs